In the electronics industry, the tendency has been to reduce the size of electronic devices such as camcorders and portable telephones while increasing performance and speed. Integrated circuit packages for complex systems typically are comprised of multiple interconnected integrated circuit chips. The integrated circuit chips usually are made from a semiconductor material such as silicon or gallium arsenide. The integrated circuit chips may be mounted in packages that are then mounted on printed wiring boards.
Typically, the packages on which these integrated semiconductor chips are mounted include a substrate or other chip-mounting device. One example of such a substrate is a leadframe. Leadframes typically include an area on which an integrated circuit chip is mounted and multiple power, ground, and/or signal leads to which power, ground, and/or signal sites of the integrated semiconductor chip are electronically attached. Semiconductor integrated chips may be attached to the leadframe using adhesive or any other techniques for attaching such chips to a leadframe which are commonly known to those skilled in the art. The power, ground and/or signal sites on the chip may then be electrically connected to individual leads of the leadframe through techniques such as wire bonding.
An interposer is an electrical interface routing between one socket or connection to another. It is an intermediate layer often used for interconnection routing or as a ground/power plane. When multiple chips are mounted within the same semiconductor package, routing problems may arise due to the different routing design of each individual chip. To solve this problem, an interposer is often used. Sometimes the terms ‘substrate’ and ‘interposer’ are used to refer to the same thing.
Leadframes have been used extensively in the integrated circuit packaging industry mainly because of their low manufacturing cost and high reliability. Leadframe packages remain a cost-effective solution for packaging integrated circuits and in recent years certain variations of leadframes such as leadless packages also emerge as improvements.
Conventional leadframes include a die pad, surrounded by a number of leads. An integrated circuit chip is attached to the die pad using a conductive adhesive such as silver epoxy. The conductive adhesive is cured after die attach. After the die is attached to the die pad, a wire-bonding process is typically used to make electrical interconnections between the integrated circuit and the leads of the leadframe. After wire bonding, the leadframe with the integrated circuit attached is encapsulated using a mold compound.
Such enclosures may include encapsulant in a plastic or a multi-part housing made of plastic, ceramic, or metal. The enclosure protects the leadframe and the attached chip from physical, electrical, and/or chemical damage. Finally, post mold curing and singulation steps are conducted to complete the packaging process.
The leadframe and attached chip(s) may then be mounted on, for example, a circuit board, or card along with other leadframes or devices. The circuit board or card may then be incorporated into a wide variety of devices such as computers, automobiles, and appliances, among others.
A problem with the conventional leadframes is that the die pad and the leads of the leadframe occupy space of the semiconductor package that is not occupied by the attached semiconductor chip, resulting in reduced chip packaging density. As integrated circuits have become smaller with increased performance requirements, enhancing packaging density becomes more and more important.
Another problem with the conventional leadframes is that it does not include many desirable passive devices, such as inductors, capacitors, and resisters, for a semiconductor package. The modern trend of integrated circuits has been that more and more functionalities, including passive device functionalities, are integrated into one single package.
Thus, a need still remains for increasing the packaging density of the leadframe design and adding passive devices to the leadframes. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures, adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.